Hot pressing is a well-known method for densifying ceramic materials. Typically, a green ceramic to be densified is placed into a die as a powder or preform. Heat and pressure are then applied to the ceramic to cause the ceramic to densify.
The atmosphere used during hot pressing may vary according to the ceramic composition being pressed. Alumina and alumina-based ceramic composites are often pressed in air or other oxygen-containing atmospheres.
For hot pressing certain alumina composites such as those produced by reaction processing techniques, there may be inadequate grain boundary mobility within the composite to allow for breakdown of large inhomogeneities often present in those composites. Accordingly, hot pressed alumina composites of the prior art may be apt to contain large voids which degrade the mechanical properties of the composite.
Thus, there exists a need to facilitate the breakup of such large voids and to generally promote more complete densification under less severe hot pressing conditions for alumina-containing ceramics in general.